The present invention relates to novel thermoplastic nonfunctional polyurethanes and to novel adhesive compositions containing these polyurethanes together with heat-reactive resol phenolic resins and vinyl solution polymers. The adhesives are useful for laminating plastic and particularly vinyl films to metal at lower activating temperatures than previously available adhesives.
Vinyl/urethane/phenolic adhesive compositions have been commercially available for some time and are known to be useful for laminating vinyl films to metal and to be operable at somewhat lower activation temperatures than other adhesives suitable for this purpose. However, even these relatively low temperature activating adhesives have been found unsatisfactory for the recently introduced thin film vinyl laminates. These new laminates differ from the standard 10 mil or thicker products in that they employ six mil or thinner vinyl films. Such thin films are substantially lower in cost per unit of area than the thicker vinyl films previously in use but cannot tolerate the 375.degree. to 425.degree. F. and higher peak metal laminating temperatures typically employed without losing their embossing, or distortion of the wood grain or other decorative pattern. Consequently laminating temperatures of no more than about 300.degree. F. may be used with such thin vinyl films.